Pfizer Inc. (NYSE: PFE) today announced that the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended has expired with respect to Pfizer's pending acquisition of Medivation, Inc.

The securities litigation law firm of Brower Piven, A Professional Corporation, has commenced an investigation into possible breaches of fiduciary duty and other violations of state law by the Board of Directors of...